There is available an exposure apparatus, such as a stepper, which projects, onto a wafer, a pattern drawn on a mask or a reticle for manufacturing semiconductor devices (see, e.g., Japanese Patent No. 3,145,355). This type of exposure apparatus has a function of aligning a wafer and a reticle before exposure. There are generally two types of alignment methods, a step and repeat type method, and a step and scan type method. The step and repeat type method measures a shift between a master, such as a reticle bearing a pattern for exposure, and an object to be exposed (substrate), such as a wafer, and repeatedly steps the object to be exposed on the basis of the measurement result, thereby performing exposure. The step and scan type method moves the master and the object to be exposed relative to each other, thereby performing exposure. These exposure apparatuses are required in terms of resolution and overlay accuracy to align at extremely high precision a wafer stage, which moves while holding an object to be exposed (e.g., a wafer). In recent years, high-speed alignment has been demanded in order to increase the productivity.
FIG. 7 is a perspective view showing a conventional wafer stage in an exposure apparatus. In FIG. 7, a Y stage 54 serving as a moving mechanism in the Y direction is mounted on a stage surface plate 55. An X stage 51 serving as a moving mechanism in the X direction is mounted on the Y stage 54. In this manner, the Y stage 54 and X stage 51 constitute an X-Y stage 56.
FIG. 8 is a schematic view showing the arrangement of the X-Y stage. The stage surface plate has a reference plane whose upper surface is smooth. The X-Y stage 56 comprises the Y stage 54 (54a, 54b, 54c, and 54d) serving as a moving member and X stage 51 serving as a moving member. A fixed guide 52 is provided in the horizontal direction (Y-axis direction) of the Y stage 54. Porous hydrostatic air bearings are provided in the horizontal direction (X-axis direction) of the X stage 51, the vertical direction (Z-axis direction) of the X stage 51, the horizontal direction (Y-axis direction) of the Y stage 54, and the vertical direction of the Y stage 54, respectively, to guide the stages.
The Y stage 54 levitates from the stage surface plate 55 by supplying air to the hydrostatic air bearings. The Y stage 54 moves by the driving actuators 54c on both sides of the stage surface plate 55 in the Y direction along the fixed guide 52 on one side. The X stage 51 levitates from the stage surface plate 55 by supplying air to the hydrostatic air bearings, similarly to the Y stage 54. The X stage 51 moves by a driving actuator 51c in the X direction using the side surfaces 54b of the Y stage 54 as a horizontal guide. At this time, a plurality of pressure applying magnetic units (not shown) adjust the X stage 51 and Y stage 54 so as to maintain respective constant postures.
FIG. 9 is a schematic view showing the arrangement of a fine adjustment stage 90. The X-Y stage 56 (see FIG. 8) having a reference plane which exerts a thrust or an attraction force on the fine adjustment stage 90 is arranged below the fine adjustment stage 90. The fine adjustment stage 90 is mounted in non-contact with a stage base 50′ on the X stage 51. The X-Y stage 56 has linear motors 11, 12 and 13, which finely control the posture of the fine adjustment stage 90 with respect to the reference plane, and cylindrical electromagnet units 21, 22 and 23, which transmit acceleration in the X and Y directions to the fine adjustment stage 90. The fine adjustment stage 90 also comprises a self-weight compensating mechanism 3 for supporting its own weight.
With this arrangement, a thrust can be applied by the linear motors 11, 12, and 13 from the X-Y stage 56 to the fine adjustment stage 90. A large attraction force in the X and Y directions can be applied by the electromagnet units 21, 22, and 23.
When the fine adjustment stage 90 is supported in non-contact with the X-Y stage 56, the linear motors 11, 12, and 13 are required to have the capability to accelerate the fine adjustment stage 90 at a desired acceleration. For this reason, the linear motors 11, 12, and 13 are predicted to generate heat in driving the fine adjustment stage 90. To cope with this, the linear motors 11, 12, and 13 have cooling mechanisms. The cooling mechanisms suppress external leakage of heat generated in the linear motors 11, 12, and 13.
FIG. 10 is a schematic view showing a linear motor coil 113, which is arranged on a support surface 100′ of the stage base 50′ to drive the fine adjustment stage 90, and a component 1, which comprises a cooling mechanism for cooling the linear motor coil 113. The component 1 is generally formed by covering the linear motor coil 113 with a jacket 112 and is arranged to supply a cooling medium into the jacket 112 using a resin tube 111. With this arrangement, the component 1 can cool the linear motor coil 113. As shown in FIG. 10, each of the ends of the resin tube 111 is shown as being truncated, merely for illustrative convenience. The ends, however, are not connected to and do not enter inside the stage base 50′.
As for the electromagnet units 21, 22, and 23 shown in FIG. 9, a large attraction force is applied to the fine adjustment stage 90 when driving the X-Y stage 56 shown in FIGS. 7 and 8. For this reason, the coils of the electromagnet units 21, 22, and 23 are also predicted to generate heat. Providing a cooling mechanism for the coils of the electromagnet units 21, 22, and 23 in the same manner as that for the linear motors 11, 12, and 13 can suppress external leakage of heat generated in the coils. Similar to the linear motors, each of the cooling mechanisms is formed by covering its coil with a jacket and is arranged to supply a cooling medium into the jacket using the resin tube 111.
A conventional stage apparatus which distributes and supplies through resin tubes a cooling medium to components having cooling mechanisms coupled to a fine adjustment stage has the following problems.
(1) If each resin tube is fixed and arranged on a stage base so as to prevent vibration of the resin tube, the size of a mounting portion for mounting the resin tube increases, and the mounting portion may interfere with surrounding components or may increase in mass.
(2) Guiding the resin tubes increases disturbance and interferes with high-precision alignment.
If the stage apparatus is placed in a vacuum chamber and used in a vacuum environment or a reduced-pressure environment, outgassing occurs in a large quantity from the resin tubes. This may cause contamination (adhesion of a contaminant) or may decrease the vacuum degree in the vacuum chamber.